Interior Permanent Magnet Motor Rotor with Mixed Ferrite and Rare-Earth Magnets
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Solution Overview
Problem
Interior permanent magnet motors face irreversible demagnetization due to armature reaction, which can be mitigated by removing magnets from the outer rotor portion, but this reduces magnetic flux and power output.
Innovation Solution
The motor design incorporates ferrite permanent magnets in the inner rotor portion and rare-earth permanent magnets in the outer portion, with specific recess sizes and arrangements to prevent demagnetization while maintaining power, using partitions to secure the magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If permanent magnets are embedded in the outer portion of the rotor, then magnetic flux is increased, but irreversible demagnetization occurs due to armature reaction
Solution Approach 1:
The patent applies local quality by using different types of permanent magnets in different regions of the rotor. Ferrite magnets with high coercivity are placed in the outer portion where armature reaction is strongest, while rare-earth magnets are placed in the inner portion. This regional differentiation allows each magnet type to be optimally positioned according to its magnetic properties, preventing demagnetization in high-stress areas while maintaining overall magnetic flux.
2Reliability
If permanent magnets are removed from the outer rotor portion to prevent demagnetization, then magnet stability is improved, but power output decreases due to reduced magnetic flux
Solution Approach 1:
The patent employs composite materials by combining two different types of permanent magnets (ferrite and rare-earth) within the same rotor structure. This composite approach allows the system to leverage the high coercivity of ferrite magnets for stability in outer regions while utilizing the superior magnetic flux density of rare-earth magnets in inner regions, thereby maintaining power output while ensuring magnet stability.
3Ease of manufacture
If ferrite permanent magnets are used in the inner rotor portion, then manufacturing cost is reduced, but magnetic flux density decreases compared to rare-earth magnets
Solution Approach 1:
The patent applies local quality by strategically positioning ferrite magnets in the inner rotor portion where the magnetic field stress is lower, and rare-earth magnets in the outer portion where higher flux density is needed. This spatial optimization allows the use of cost-effective ferrite magnets without significantly compromising overall magnetic flux density, while rare-earth magnets provide the necessary flux enhancement in critical regions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively prevents irreversible demagnetization and maintains power output by strategically placing ferrite and rare-earth magnets within the rotor, ensuring magnetic flux is preserved and power is compensated.
Implementation Method 1
a stator having teeth on which a coil is wound; a rotor rotatably provided inside the stator, the rotor including a plurality of rotor sectors; at least two permanent magnet recesses formed between the rotor sectors; ferrite permanent magnets embedded in predetermined ones of the permanent magnet recesses that are formed in an inner portion of the rotor; and rare-earth permanent magnets embedded in the other ones of the permanent magnet recesses that are formed in an outer portion of the rotor
Data Source
AI summary
An interior permanent magnet motor includes a stator having teeth on which a coil is wound, a rotor rotatably provided inside the stator, the rotor including a plurality of rotor sectors, and at least two permanent magnet recesses formed between the rotor sectors. Ferrite permanent magnets are embedded in predetermined ones of the permanent magnet recesses that are formed in an inner portion of the rotor. Rare-earth permanent magnets are embedded in the other ones of the permanent magnet recesses that are formed in an outer portion of the rotor.